#include <stdio.h>
#include <omp.h>
 
int main() {
    long long n = 100000000; // Number of terms
    double pi = 0.0;
 
    // Start the parallel region
    #pragma omp parallel
    {
        double sum = 0.0;
        // Use a private variable for each thread
        #pragma omp for
        for (long long k = 0; k < n; k++) {
            // Calculate the term and accumulate in the private sum
            sum += (k % 2 == 0 ? 1.0 : -1.0) / (2.0 * k + 1.0);
        }
 
        // Combine results from all threads
        #pragma omp atomic
        pi += sum;
    }
 
    pi *= 4; // Multiply by 4 to get the final value of π
 
    printf("Approximation of PI: %.15f\n", pi);
    return 0;
}

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